Some novel approaches to the assessment of beer quality
Madigan, David (1996) Some novel approaches to the assessment of beer quality. PhD thesis, Dublin City University.
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The shelf-life of a packaged beer is determined by its ability to resist detrimental changes to its flavour, aroma and clarity. The most common symptoms of beer deterioration are the development of colloidal (non-biological) haze, formation of offflavours, precipitation of sediment, and, in extreme cases, the growth of spoilage organisms. The susceptibility of a beer to spoilage by any of these mechanisms may be predicted by measurement of appropriate indicator compounds. The aim of this thesis was to develop new or improved liquid chromatographic methods for the determination of these compounds, using selective detection systems which allowed direct injection of samples following dilution and/or clarification. Where appropriate, these methods were applied to the development of optimised stabilisation protocols.
The area studied in greatest detail was the application of analytical technology to the investigation of beer colloidal stability. Novel methods for the determination of flavanols in beer were developed, and new procedures for the isolation of flavanol standards were described. These methods were then applied to the detailed study of the role of these compounds in beer haze and flavour instability. The stabilisation process was also studied in detail, and optimised stabilisation protocols were recommended.
Volatile phenolics in beer were also studied. Novel methods for the determination of phenolic-off-flavour (POF) causing compounds were developed, and were applied to the optimisation of brewing regimes as well as to the classification of POF-producing yeasts.
Oxalate may cause hazes and sediments in beers. A method was therefore developed for the determination of soluble and insoluble oxalate in beer and beer sediments, and the factors leading to the formation of such sediments were examined with a view to recommending procedures which could prevent the incidence of oxalate complaints in beer.
Novel analytical methods using electrochemical detection were also developed for the determination of carbohydrates in beers, worts and non-alcoholic beverages, and for the determination of ascorbic acid in beer and malt beverages. These methods were then applied to the assessment of beer quality in general.
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